JP2015078942A - Leakage magnetic flux flaw detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an inclination angle in the longitudinal direction of flaw, which is formed on the surface of an object to be inspected of a magnetic material, over a range from 0° to ±90 when leakage magnetic flux flaw detection is performed.SOLUTION: An operation part 14 causes a measuring apparatus 12 to two-dimensionally scan the surface of an object 24 to be inspected. During scanning, from at least one of an amplitude component and a phase component of a leakage magnetic flux detected by a magnetic sensor 22 of the measuring apparatus 12, a plurality of two-dimensional distributions are obtained in which respective different characteristics of the leakage magnetic flux are reflected. Furthermore, in the operation part 14, based on these two dimensional distributions, an inclination angle θ in the longitudinal direction of flaw 34 formed on the surface of the object 24 to be inspected is calculated.

Description

  The present invention relates to a leakage magnetic flux flaw detector.

  2. Description of the Related Art Conventionally, a leakage magnetic flux flaw detector is known as means for detecting a flaw on the surface of an inspection object of a magnetic material.

  As shown in FIG. 26, when the inspection object 100 is magnetized when the scratch 102 is formed on the inspection object 100, the magnetic flux flowing through the inspection object 100 leaks into the air so as to straddle the damage 102. . By providing the magnetic sensor 104 on the surface of the inspection object 100 and detecting the leakage magnetic flux 106, the position of the scratch on the inspection object 100 can be specified.

  Furthermore, each characteristic of the flaw 102 can be calculated based on each characteristic of the detected leakage magnetic flux 106. For example, in Non-Patent Document 1, two magnetic sensors whose detection axes are orthogonal to each other are scanned on the inspection object, and the amplitude components of the leakage magnetic flux are respectively obtained. Further, based on these amplitude components, the inclination angle in the longitudinal direction of the scratch is obtained.

  Further, in Patent Document 1, a magnetic sensor is scanned over an inspection object, and a reception signal of the magnetic sensor is synchronously detected, and a component having the same phase as the reference signal and a phase component delayed by 90 ° from the reference signal are obtained. Ask. Further, both components are plotted on the XY plane, and the inclination angle in the longitudinal direction of the scratch is obtained from the locus.

JP 2008-128733 A

Uetake, “Quantitative evaluation system for surface flaws in magnetic flux leakage test,” Nondestructive Inspection, Japan Nondestructive Inspection Association, November 1992, Vol. 41, No. 11, p. 657-664

  By the way, in the conventional leakage magnetic flux flaw detector, it is difficult to detect the scratch angle over the entire range from 0 ° (parallel to the scanning direction) to ± 90 °. For example, in Non-Patent Document 1, although described in the document, it is difficult to evaluate the angle of a scratch having an angle of 15 ° or less with respect to the scanning direction. Also, in Patent Document 1, it is difficult to evaluate the angle of a scratch having an angle of 75 ° or more with respect to the scanning direction, clearly from the examples. Accordingly, an object of the present invention is to provide a leakage magnetic flux flaw detector capable of detecting the angle of a scratch over a range from 0 ° to ± 90 °.

  The present invention relates to a leakage magnetic flux flaw detector. The apparatus includes a magnetizing unit that applies an alternating magnetic field to an inspection object of a magnetic material, a magnetic sensor that is fixed with respect to the magnetization unit and detects a leakage magnetic flux from the surface of the inspection object, With a measuring instrument. Further, when the measuring device is scanned two-dimensionally on the surface of the inspection object, different characteristics of the leakage magnetic flux are obtained from at least one of the amplitude component and the phase component of the leakage magnetic flux detected by the magnetic sensor. A plurality of two-dimensional distributions that are reflected are calculated, and an arithmetic unit that calculates an inclination angle in a longitudinal direction of a flaw formed on the surface of the inspection object is provided based on the two-dimensional distribution.

  In the above invention, it is preferable that the calculation unit obtains a two-dimensional distribution of an amplitude component and a phase component of leakage magnetic flux.

  In the above invention, it is preferable that the calculation unit calculates the inclination angle of the scratch based on a change rate of adjacent phase components on the two-dimensional distribution of the phase components.

  In the above invention, it is preferable that the calculation unit calculates the inclination angle of the scratch based on an inclination angle of a line segment connecting the maximum value and the minimum value of the change rate of the phase component.

  In the above invention, it is preferable that the calculation unit calculates the inclination angle of the scratch based on an isoline shape on a two-dimensional distribution of the amplitude component.

  In the above invention, the magnetic sensor detects a detection axis direction component of leakage magnetic flux along a detection axis of the magnetic sensor, and the calculation unit uses the two-dimensional distribution of the amplitude component to detect the detection. An angle of inclination with respect to the axis is calculated within a first angle range, and the second angle difference between the angle with respect to the detection axis and the first angle range is calculated using a two-dimensional distribution of the phase component. It is preferable to calculate the inclination angle of the scratch within the angle range.

  In the above invention, it is preferable that the first angle range is 45 ° to 90 °, and the second angle range is 0 ° to 45 °.

  According to the present invention, the inclination angle of the scratch on the surface of the inspection object can be detected over a range from 0 ° to ± 90 °.

It is a figure which illustrates the leakage magnetic flux flaw detector which concerns on this embodiment. It is a figure which illustrates the measurement probe which concerns on this embodiment. It is a schematic diagram explaining the principle of leakage magnetic flux flaw detection. It is a schematic diagram explaining the principle of leakage magnetic flux flaw detection. It is a schematic diagram explaining the principle of leakage magnetic flux flaw detection. It is a schematic diagram explaining the principle of leakage magnetic flux flaw detection. It is a figure explaining the sample which performs a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure explaining the calculation method of the inclination-angle of a crack. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure which shows the result of a leakage magnetic flux flaw detection. It is a figure explaining the calculation method of the inclination-angle of a crack. It is a figure which shows the calculation precision of a leakage magnetic flux flaw. It is a figure explaining the principle of leakage magnetic flux flaw detection.

  FIG. 1 illustrates a leakage magnetic flux flaw detector 10 according to this embodiment. The leakage magnetic flux flaw detector 10 includes a measuring instrument 12 and a calculation unit 14.

  The measuring instrument 12 includes a measuring probe 15, a moving stage 16, and a stage controller 18. The moving stage 16 fixes the inspection object 24 and moves the measurement probe 15. The moving stage 16 may be a three-axis stage. For example, the measurement probe 15 is moved in three axial directions, ie, the Z axis that is the vertical direction, the X axis that is orthogonal to the Z axis (in the horizontal plane), and the Y axis that is orthogonal to the X axis and the Z axis. Good.

  As will be described later, in order to obtain a two-dimensional distribution related to the inspection object 24, the inspection object 24 and the measurement probe 15 need only be relatively moved. Therefore, the moving stage 16 fixes the measurement probe 15 to each other. In this case, the inspection object 24 may be moved. From this, the aspect of “scanning the measurement probe 15 on the surface of the inspection object 24” means that when the inspection probe 24 is fixed and the measurement probe 15 is moved, the measurement probe 15 is fixed and the inspection object is fixed. In the case of moving 24, both of the cases of moving both may be included. Note that when acquiring the two-dimensional distribution related to the inspection object 24, the measurement probe 15 is often smaller and lighter than the inspection object 24. It is preferable to adopt a mode in which 24 is fixed and the measurement probe 15 is moved.

  The stage controller 18 is an operation unit that gives an operation command to the moving stage 16. The stage controller 18 may receive a command from the calculation unit 14 and operate the moving stage 16. Further, the stage controller 18 and the moving stage 16 may be integrated.

  As shown in FIG. 2, the measurement probe 15 includes a magnetizer 20 and a magnetic sensor 22. The measurement probe 15 may include a non-magnetic holder that holds the magnetizer 20 and the magnetic sensor 22. Further, a constant current circuit for supplying an AC constant current to the magnetizer 20 may be provided.

  The magnetizer 20 is a magnetizing unit that applies an alternating magnetic field to the inspection object 24 made of a magnetic material. The alternating magnetic field may be an alternating magnetic field in which the poles are switched during one cycle, or may be a magnetic field whose magnitude is changed without switching the poles.

  As shown in FIG. 2, the magnetizer 20 includes a core 26 and a coil 28. The core 26 may have a U shape including a bridge portion 32 that connects the two arm portions 30A and 30B and the arm portions 30A and 30B. The core 26 is made of a high magnetic permeability magnetic material, for example, 45NiFe, a laminated silicon steel plate, or ferrite. The end surfaces of the arm portions 30A and 30B are preferably adapted to the shape of the surface of the inspection object 24. For example, when the surface of the inspection object 24 is a plane, it is preferable that the end surfaces of the arm portions 30A and 30B are also a plane. For example, the flatness of the end surface may be 0.05 mm or less.

  Further, the weight and size of the magnetizer 20 are those that can be easily scanned by the moving stage 16, that is, are preferably small. For example, the weight is 150 g or more and 200 g, and the longitudinal direction thereof. The length L is 30 mm to 40 mm, the lateral width W is 15 mm to 25 mm, and the height H is 15 mm to 25 mm. The distance D between the arm portions 30A and 30B may be any distance as long as the magnetic sensor 22 can be disposed, and is, for example, 11 mm or more and 12 mm or less.

  The coil 28 is an exciting member that is wound around the core 26. In order to generate an alternating magnetic field, the coil 28 is supplied with an alternating constant current. The coil 28 may be wound around the arm portions 30 </ b> A and 30 </ b> B and the bridge portion 32 of the core 26, for example. The wire diameter of the coil 28 is, for example, 0.15 mm, and the number of turns is, for example, 165 turns.

  The magnetic sensor 22 detects leakage magnetic flux from the surface of the inspection object. The magnetic sensor 22 may be, for example, a magnetic impedance (MI) sensor, a magnetoresistive effect (MR) sensor, or a Hall element. For example, when the magnetic sensor 22 is composed of a magnetic impedance sensor, the magnetic sensor 22 outputs a voltage signal corresponding to the strength of the leakage magnetic flux.

  The magnetic sensor 22 is configured to detect only a magnetic component in a specific direction, and an axis along this detection direction is hereinafter referred to as a detection axis. For example, the magnetic sensor 22 is fixed at an intermediate position between the arm portions 30A and 30B so that the detection axis A is parallel to the longitudinal direction of the bridge portion 32 (in the lower part of FIG. 2, parallel to the X axis). By doing so, around the magnetic sensor 22, the magnetization direction by the magnetizer 20 and the detection axis of the magnetic sensor 22 coincide (become parallel).

  The magnetic sensor 22 is fixed to the magnetizer 20 by, for example, assembling the magnetic sensor 22 to a substrate and fixing the substrate to the core 26 with a resin screw or the like. Thus, by fixing the position of the magnetic sensor 22 with respect to the magnetizer 20, it is possible to prevent the two from moving relative to each other during measurement. Moreover, it is preferable that the bottom surface of the magnetic sensor 22 is arranged substantially in the same plane as the end surfaces of the arm portions 30A and 30B of the magnetizer 20. For example, the position crossing in the Z-axis direction (vertical direction) between the end surface and the bottom surface of the magnetic sensor 22 may be 0.02 mm.

  FIG. 3 shows a schematic diagram of detection of leakage magnetic flux by the magnetic sensor 22. When an alternating magnetic field is applied to the inspection object 24 by the magnetizer 20, a magnetic flux flows in the inspection object 24 as shown by hatching. At this time, when the scratch 34 is formed on the surface of the inspection object 24, the end surface of the scratch 34 forms a pole in the magnetic field, and the magnetic flux leaks into the air between the magnetic poles. The magnetic sensor 22 detects this leakage magnetic flux B.

  As shown in the upper part of FIG. 4, the leakage magnetic flux B is generated radially in the air with the wound 34 as the center. From this, the direction and magnitude of the detected leakage magnetic flux B differ depending on the relative position between the magnetic sensor 22 and the scratch 34. The position of the flaw 34 can be specified using the change in the direction and size of the detected leakage magnetic flux B. For example, in the present embodiment, the detection axis A of the magnetic sensor 22 is set to be parallel to the surface of the inspection object 24. From this, the magnetic sensor 22 detects the horizontal component Bx of the leakage magnetic flux B.

The lower part of FIG. 4 shows changes in the strength of the magnetic flux detected by the magnetic sensor 22 for each relative position between the scratch 34 and the magnetic sensor 22. The horizontal component Bx of the leakage magnetic flux shows an upwardly convex quadratic locus, and takes a local maximum value when the magnetic sensor 22 is positioned directly above the scratch 34. Therefore, the value of the magnetic sensor 22 corresponding to the scanning of the measurement probe 15 is monitored, and it can be seen that the scratch 34 is formed at the position where the maximum value is obtained. The solid curve in the lower part of FIG. 4 indicates the locus of the vertical component B _Z of the leakage magnetic flux B.

  Returning to FIG. 1, the calculation unit 14 includes a detector 36 and a calculation processor 38. The detector 36 and the arithmetic processor 38 may be integrated into a single device.

  The detector 36 extracts a desired signal from the signal (voltage signal) detected by the magnetic sensor 22. For example, the detector 36 acquires at least one of an amplitude component and a phase component from the signal detected by the magnetic sensor 22. Here, the phase component indicates a phase difference component (α) of a received signal (for example, Sin (ωt + α)) with respect to a reference signal (for example, Sin (ωt)). The detector 36 may be a lock-in amplifier, for example. The reference signal of the lock-in amplifier may be an alternating current (excitation current) supplied to the coil 28.

  The arithmetic processor 38 calculates the inclination angle θ of the flaw 34 by performing arithmetic processing on the signal acquired by the detector 36. Further, the arithmetic processor 38 transmits an operation command for the measurement probe 15 to the stage controller 18. The arithmetic processor 38 may include an arithmetic circuit, and may be a computer, for example.

  The processor 38 causes the measurement probe 15 to scan the surface of the inspection object 24 two-dimensionally via the stage controller 18. For example, the measurement probe 15 is scanned from one end to the other end of the inspection object 24 in the X-axis direction, and when reaching the other end, the predetermined width measurement probe 15 is shifted in the Y-axis direction, and the measurement probe 15 is scanned again on one end side. Let In this scanning, it is preferable that the magnetization direction and the direction of the detection axis of the magnetic sensor 22 with respect to the magnetization direction are constant with respect to the inspection object 24. For example, the measurement probe 15 is prevented from rotating around the Z axis during scanning in the X axis direction and the Y axis direction.

  Further, as will be described below, the arithmetic processor 38 obtains a two-dimensional distribution of at least one of the amplitude component and the phase component of the leakage magnetic flux acquired from the magnetic sensor 22, and from the two-dimensional distribution, the inspection object 24 is obtained. The inclination angle θ of the upper scratch 34 is obtained.

  FIG. 5 illustrates a plan view of the inspection object 24. Also, in this figure, arm portions 30A and 30B of the magnetizer 20 are also shown in order to show the magnetization direction. Focusing on the central portions of the arm portions 30A and 30B, the magnetization direction extends linearly from one arm portion 30A to the other arm portion 30B.

  A scratch 34 is formed on the surface of the inspection object 24. The scratch 34 is inclined at an angle θ with respect to the detection axis A (and the magnetization direction) of the magnetic sensor 22. This angle θ (the angle of the longitudinal direction of the scratch 34 with respect to the detection axis) is hereinafter referred to as an inclination angle. The horizontal component Bx (component parallel to the magnetization direction and the detection axis of the magnetic sensor 22) of the leakage magnetic flux B straddling the flaw 34 changes according to the inclination angle θ of the flaw 34.

FIG. 6 shows how the horizontal component Bx of the leakage magnetic flux B changes according to the inclination angle θ of the scratch 34. The horizontal axis is the tilt angle θ, and the vertical axis is the ratio Bx ₍ θ of the horizontal component Bx of the leakage magnetic flux at the predetermined tilt angle θ to the horizontal component Bx at the tilt angle θ = 90 ° (perpendicular to the magnetization direction). ₎ / Bx ₍₉₀ ^° ₎ . According to this, as the inclination angle θ decreases, the horizontal component Bx of the leakage magnetic flux decreases. That is, the horizontal component Bx of the leakage magnetic flux is different if the inclination angle θ is different in spite of the scratch 34 having the same width and depth. Therefore, if the state of the flaw 34 is to be grasped only from the horizontal component Bx of the leakage magnetic flux, an erroneous calculation result that the width is narrower than the actual flaw 34 or the flaw is shallow may be derived.

Here, it is known that the curve indicating the decreasing process of the horizontal component Bx is represented by Sin ² θ. Therefore, if the inclination angle θ of the scratch 34 is known, the value of the horizontal component Bx of the leakage magnetic flux detected by the magnetic sensor 22 can be corrected. Therefore, the calculation unit 14 obtains the inclination angle θ of the scratch 34 as follows.

  First, the arithmetic processor 38 obtains a two-dimensional distribution of at least one of the amplitude component and the phase component of the horizontal component Bx of the leakage magnetic flux detected by the magnetic sensor 22. For example, the arithmetic processor 38 acquires the amplitude component and the phase component of the horizontal component Bx of the leakage magnetic flux through the detector 36. At the same time, the processor 38 acquires the current position coordinates of the measurement probe 15 based on the operation command to the stage controller 18. Furthermore, the arithmetic processor 38 associates these position coordinates with the amplitude component and the phase component and stores them in a storage unit (not shown).

  Further, the arithmetic processor 38 generates a two-dimensional distribution diagram of amplitude components on arbitrary plane coordinates using the position coordinates and amplitude component data stored in the storage unit. Similarly, the arithmetic processor 38 generates a two-dimensional distribution diagram of phase components on arbitrary plane coordinates. It is preferable that the plane coordinates be determined so that the horizontal axis direction (X direction) is parallel to the detection axis and the vertical axis direction (Y direction) is orthogonal to the detection axis.

  8 to 14 illustrate two-dimensional distributions of amplitude components. In obtaining these two-dimensional distributions, a sample of the inspection object 24 shown in FIG. 7 was used. The inspection object 24 is made of SS400 steel plate, and has a plate thickness of 5 mm, a width of 100 mm, and a depth of 120 mm. Further, an artificial scratch 34 was formed at the center of the surface of the inspection object 24. The scratch 34 had a width of 0.15 mm, a length of 5.0 mm, and a depth of 1.0 mm. Note that the scratches 34 were formed so that the width direction of the SS400 steel plate was the longitudinal direction.

  Furthermore, in the measurement, the distance between the end faces of the arm portions 30A and 30B of the magnetizer 20 and the surface of the inspection object 24 was set to 0 mm (contact). The alternating current supplied to the coil 28 was a sine wave of 100 Hz and 20 mA. 8 to 24, the center of the two-dimensional distribution is made coincident with the center of the scratch 34.

  The inclination angle θ of the scratch 34 with respect to the detection axis (parallel to the magnetization direction) of the magnetic sensor 22 is set between 0 ° and 90 °, and the measurement probe 15 is placed on the inspection object 24 at each angle. Let it scan. FIG. 8 to FIG. 14 show the two-dimensional distribution of the amplitude components obtained for each angle.

  FIG. 8 shows a two-dimensional distribution of the amplitude component of the horizontal component Bx of the leakage magnetic flux when the tilt angle θ = 0 °, that is, when the longitudinal direction of the scratch 34 is parallel to the detection axis (and the magnetization direction). Similarly, in FIGS. 9, 10, 11, 12, 13, and 14, the inclination angle θ is 15 °, 30 °, 45 °, 60 °, 75 °, and 90 ° (that is, the length of the scratch 34). A two-dimensional distribution of amplitude components when the direction is perpendicular to the detection axis is shown. In both figures, the hatched dense area indicates that the amplitude component value is relatively large, and the hatched sparse area indicates that the amplitude component value is relatively small. Yes.

  Referring to FIGS. 11 to 14, that is, the two-dimensional distribution when the inclination angle θ is 45 ° to 90 °, the shape of the isoline surrounding the relatively large region is a substantially elongated elliptical shape. . Moreover, the major axis of the ellipse shows good agreement with each inclination angle. From this, the arithmetic processor 38 calculates the inclination angle θ in the longitudinal direction of the flaw 34 based on the shape of the isoline.

  As shown in FIG. 15, an arbitrary ellipse shape surrounded by an isoline of a two-dimensional distribution is specified, and the major axis is acquired. The ellipse shape to be specified may be an ellipse shape formed by an arbitrary isoline showing a value of 70% to 100% of the maximum value of the amplitude component of the two-dimensional distribution. In addition, since the shape surrounded by the isolines is often not an accurate elliptical shape, the major axis may be obtained after approximating the elliptical shape.

After obtaining the major axis of the ellipse, the arithmetic processor 38 obtains the inclination angle θ. Specifically, as shown in FIG. 15, the length component x _L0 in the X direction and the length component y _L0 in the Y direction of the major axis L0 are obtained, and θ = tan ⁻¹ (y _L0 / x _L0 ). The inclination angle θ is obtained.

  Next, a process for obtaining the tilt angle θ from the two-dimensional distribution of phase components will be described. The arithmetic processor 38 creates a two-dimensional distribution for the phase component in the same manner as the amplitude component. 16 to 22, the longitudinal inclination angle θ of the scratch 34 is set to 0 °, 15 °, 30 °, 45 °, 60 °, 75 °, and 90 ° in the same manner as in FIGS. 8 to 14. A two-dimensional distribution diagram of each phase component is shown. For the inspection object, the inspection object 24 shown in FIG. 7 was used in the same manner as the amplitude component. In each of the figures, as in FIGS. 8 to 14, the hatched dense region indicates that the phase component value is relatively large (the phase difference from the reference signal is large). The sparse region indicates that the value of the phase component is relatively small.

  Here, FIG. 23 shows a distribution diagram obtained by processing the two-dimensional distribution of FIG. This figure shows the change rate of adjacent phase components on the two-dimensional distribution. Specifically, the differential value in the X direction in the figure is obtained and plotted on the plane coordinates. In other words, FIG. 23 shows the spatial first-order differentiation of the two-dimensional distribution of FIG. 19 in the X direction.

Further, as shown in FIG. 24, the center of the isoline surrounding the maximum value (the maximum value in the X-direction upward gradient) and the isoline surrounding the minimum value (the maximum value in the X-direction upward gradient) are centered. Connect with a straight line L1. It can be understood that the inclination of the straight line L1 is in good agreement with the inclination angle (= 45 °) of the scratch 34 in FIG. From this, the length component x _L1 in the X direction and the length component y _L1 in the Y direction of the straight line L1 are obtained, and the inclination angle θ is obtained by θ = tan ⁻¹ (y _L1 / x _L1 ).

  As described above, the inclination angle θ of the scratch 34 can be obtained from the two-dimensional distribution of the amplitude component and the phase component. FIG. 25 shows a graph showing the accuracy of the inclination angle θ obtained by the above calculation. In this graph, the horizontal axis indicates the actual inclination angle θ of the scratch 34, and the vertical axis indicates the error between the inclination angle obtained by calculation and the actual inclination angle. A filled diamond plot (♦) indicates the calculation result based on the two-dimensional distribution of the amplitude component, and an open circle plot (◯) indicates the calculation result based on the two-dimensional distribution of the phase component.

  As shown in this graph, for the calculation using the phase component, a highly accurate result is obtained when the inclination angle θ is in the range of 0 ° to 45 °, and for the calculation using the amplitude component, the inclination angle Highly accurate results are obtained in the range of 45 ° to 90 °. In this way, by using the two-dimensional distribution based on the phase component and the two-dimensional distribution based on the amplitude component, the inclination angle θ in the longitudinal direction of the flaw 34 is ± 0. It can be obtained with a high accuracy of 4 °. In the above embodiment, only the range from 0 ° to + 90 ° is shown, but the range from 0 ° to −90 ° can be calculated in the same manner depending on the objectivity.

  In the above embodiment, the inclination angle θ is obtained by using the two-dimensional distribution of the phase component and the amplitude component, but the present invention is not limited to this form. For example, the inclination angle θ can be obtained over a range of 0 ° to 90 ° using only the phase component or only the amplitude component.

  In this case, the magnetic sensor 22 includes a first magnetic sensor 22A and a second magnetic sensor 22B whose detection axes are orthogonal to each other, and the magnetizer 20 includes the detection axes of the magnetic sensors 22A and 22B and the magnetization direction (magnetic sensor). Are formed by two magnetizers 20A and 20B having the same direction (opposite directions of the arm portions 30A and 30B).

  As shown in the above embodiment, for example, in the case of a phase component, the inclination angle θ can be obtained with high accuracy up to 45 ° in the range of 0 ° to 90 °. From this, the inclination angle θ is detected in the range of 0 ° to 90 ° by obtaining the two-dimensional distribution of the respective phase components using the two magnetic sensors 22A, 22B with the detection axes different by 90 °. be able to.

  Specifically, the inspection object 24 is magnetized by the magnetizer 20A, the leakage magnetic flux at this time is measured by the magnetic sensor 22A, and the first angle is measured using the two-dimensional distribution of the phase component of the measured signal. An inclination angle θ within a range (for example, 0 ° to 45 °) is obtained. Further, the inspection object 24 is magnetized by the magnetizer 20B, the leakage magnetic flux at this time is measured by the magnetic sensor 22B, and the first angle range is determined using the two-dimensional distribution of the phase component of the measured signal. An inclination angle θ in a different second angle range (for example, 45 ° or more and 90 ° or less) is obtained. In this way, the inclination angle θ can be obtained over a range of 0 ° to ± 90 °. Similarly, using the magnetic sensors 22A and 22B, the inclination angle θ can be obtained over a range of 0 ° to ± 90 ° from the two-dimensional distribution of the respective amplitude components.

  In this manner, in the present embodiment, the arithmetic processor 38 has different characteristics (amplitude component and phase component, detection) of the leakage magnetic flux from at least one of the amplitude component and the phase component of the leakage magnetic flux detected by the magnetic sensor 22. A plurality of two-dimensional distributions reflecting the amplitude components obtained from the two magnetic sensors whose axes are orthogonal to each other and the phase components obtained from the two magnetic sensors whose detection axes are orthogonal to each other are obtained. Further, based on these two-dimensional distributions, the inclination angle θ in the longitudinal direction of the scratches 34 formed on the surface of the inspection object 24 is calculated over a range of 0 ° to ± 90 °.

  In the embodiment described above, in the embodiment in which the amplitude component and the phase component are extracted from one magnetic sensor 22 and the two-dimensional distribution is used, the magnetization direction to the inspection object 24 is only one direction. Therefore, the tilt angle θ of the flaw 34 can be obtained by the magnetizer 20 having a relatively simple configuration without requiring a complicated magnetizer such as applying a rotating magnetic field to the inspection object 24. Furthermore, as compared with the case where two magnetic sensors 22A and 22B are used, calibration of the output and sensitivity of each magnetic sensor is not required, and there is an advantage that a flaw detection test can be performed more easily.

  In this embodiment, when obtaining the inclination angle θ of the scratch 34, two types of two-dimensional distributions (for example, an amplitude component and a phase component) having different characteristics are obtained. For example, the following method is used.

  For example, in the case of an amplitude component, as shown in FIGS. 8 to 10, when the isoline region of the maximum value is dispersed in a plurality of places, the inclination angle θ is 0 ° <θ <45 ° with a large calculation error. Is likely to be in the range. Therefore, the arithmetic processor 38 counts the number of isoline shapes of the maximum value of the two-dimensional distribution of amplitude components, and when this is 2 or more, the arithmetic processor 38 calculates the inclination angle θ. The other two-dimensional distribution is selected without using.

  Similarly, in the case of a phase component, as shown in FIGS. 20 to 22, as the maximum isoline shape collapses from a circle, the inclination angle θ is 45 ° <θ <with a large calculation error. There is a high possibility of being in the range of 90 °. Therefore, the arithmetic processor 38 obtains the circularity of the isoline shape of the maximum value for the two-dimensional distribution of the phase component, and this exceeds a predetermined upper limit threshold (for example, 1.5) or lower limit threshold (for example, for example). If it is less than 0.5), the other two-dimensional distribution is selected without using this two-dimensional distribution for calculating the inclination angle θ.

  DESCRIPTION OF SYMBOLS 10 Magnetic flux leakage inspection apparatus, 12 Measuring instrument, 14 Computation part, 15 Measurement probe, 16 Moving stage, 18 Stage controller, 20 Magnetizer, 22 Magnetic sensor, 24 Inspection object, 26 core, 28 coil, 30A, 30B Arm part , 32 bridge section, 34 scratches, 36 detector, 38 arithmetic processor.

Claims (7)

A measuring device comprising: a magnetizing unit that applies an alternating magnetic field to an inspection object of a magnetic material; and a magnetic sensor that is fixed with respect to the magnetization unit and detects a leakage magnetic flux from the surface of the inspection object. When,
When the measuring device is scanned two-dimensionally on the surface of the inspection object, different characteristics of the leakage magnetic flux are reflected from at least one of the amplitude component and the phase component of the leakage magnetic flux detected by the magnetic sensor. Calculating a plurality of two-dimensional distributions, and based on the two-dimensional distribution, a calculation unit that calculates an inclination angle in a longitudinal direction of a wound formed on the surface of the inspection object;
A leakage magnetic flux flaw detector characterized by comprising: The leakage magnetic flux flaw detector according to claim 1,
The leakage magnetic flux flaw detector according to claim 1, wherein the calculation unit obtains a two-dimensional distribution of an amplitude component and a phase component of the leakage flux. The leakage magnetic flux flaw detector according to claim 2,
The leakage magnetic flux flaw detector according to claim 1, wherein the calculation unit calculates an inclination angle of the flaw based on a change rate of adjacent phase components on a two-dimensional distribution of the phase components. The leakage magnetic flux flaw detector according to claim 3,
The leakage magnetic flux flaw detector according to claim 1, wherein the calculation unit calculates an inclination angle of the flaw based on an inclination angle of a line segment connecting the maximum value and the minimum value of the change rate of the phase component. The leakage magnetic flux flaw detector according to any one of claims 2 to 4,
The leakage magnetic flux flaw detector according to claim 1, wherein the arithmetic unit calculates an inclination angle of the flaw based on an isoline shape on a two-dimensional distribution of the amplitude component. The leakage magnetic flux flaw detector according to any one of claims 2 to 5,
The magnetic sensor detects a detection axis direction component of leakage magnetic flux along the detection axis of the magnetic sensor,
The computing unit is
Using the two-dimensional distribution of the amplitude component, calculate the inclination angle of the scratch having an angle with respect to the detection axis within a first angle range;
Leakage magnetic flux using the two-dimensional distribution of the phase component to calculate an inclination angle of the scratch having an angle with respect to the detection axis within a second angle range different from the first angle range Flaw detection equipment. The leakage magnetic flux flaw detector according to claim 6,
The first angle range is not less than 45 ° and not more than 90 °,
The leakage magnetic flux flaw detector according to claim 2, wherein the second angle range is 0 ° to 45 °.

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